1. Field of the Invention
This invention relates to removable disk drives for computer systems, and more particularly to a security module for a removable disk drive having a lockable write protect feature, and an associated docking base.
2. Description of Related Art
In the early history of computer data storage devices, magnetic disk drives having removable magnetic platters were commonly used. This configuration of equipment permitted the use of a number of sets of platters with one drive unit, resulting in substantial economies since much of the cost of such a disk drive unit was in the motor drive unit, read/write head structure, and control electronics. Another advantage of such a configuration is that the platters could be removed and safely stored for security purposes.
One common feature of such removable platter disk drive until was a "write protect" switch that activated a hardware control system of the disk drive itself. The write protect feature prevented data from being written to the platters, thereby protecting the data on such platters from inadvertent alteration or erasure. While software could be used to provide a degree of write protection, a hardware implementation of the feature was found to be more secure from software error and international software tampering. However, a disadvantage of the prior art is that the operator was required to remember to activate the write-protect switch. Moreover, such drives did not prevent accidental or negligent deactivation of the write-protect switch.
More recently, the cost of computer disk drives has decreased dramatically to the point that the platters, drive motor, read/write head structure, and control electronics are sold as a single unit, with the platters typically hermetically sealed within the unit. With the platters sealed within the disk drive, reliability of such drives is substantially improved over disk drives with removable platters.
A disadvantage of sealed disk drives has been that they are normally not designed to be easily removed from a computer system. Such removability is desirable for a number of reasons, including ready replacement of defective drives and transportation of data from one computer system to another. However, probably the most important reasons for such removability is to permit removal of drives containing sensitive data for security purposes. In some cases, data may be so sensitive that a removed drive must be stored in a vault when not in use.
Another disadvantage of commonly available sealed drives is that they typically do not provide a dedicated, lockable write protection feature. While some drives have interfaces which include a WRITE signal line which can be trapped and blocked to emulate a write-protect input, in other drives (such as disk drives having a Small Computer System Interface), all commands are logically coded, and no provision exists for activating a dedicated write-protect input or blocking a WRITE signal without very sophisticated (and hence expensive) command monitoring and decoding.
With the advent of small format disk drives (e.g., commonly available 51/4" and 31/2" form factor drives), a number of removable disk drives have been introduced. Some of these products include a "docking base" coupled to a computer system and having a power supply and computer interface, with the disk drive itself being removable from the docking base. In other products, the disk drive, power supply, and computer interface form a removable unit, although the computer system may have a "docking interface" for making electrical connections to the removable unit.
However, a continuing disadvantage of such removable drives is that they do not provide a lockable, hardware write protection feature.
It is therefore desirable to provide a removable disk drive unit having a lockable, hardware write protection feature. It is also desirable to provide a locking switch mechanism for controlling the write protection feature, in order to provide better security for the system. The present invention meets these needs as well as providing other desirable features and functions.